Our objective is to carry out a Phase I clinical trial with a second generation immunotoxin (IT) prepared with a murine monoclonal anti-CD25 antibody, attached via a stable crosslinker (SMPT) to deglycosylated ricin A chain (dgA). The aims will be to determine the toxicity, immunogenicity, tumor localization, pharmacokinetics and clinical benefit of this IT in patients with refractory CD25+ neoplasms such as T cell lymphoma, CLL, NHL, HCL and Hodgkin's disease. Results will be evaluated in relation to CD25 (p55) expression. To this end we will prepare the IT and carry out quality control studies in our GLP laboratory. The data will be used to file an IND. Patients will then be treated in an open label, Phase I dose escalation protocol until MTD is established. Should this IT prove to be safe and of any clinical benefit, further trials will be warranted.